RF transceiver front end module with improved linearity

Abstract

A power amplifier system front end measures both forward and reverse power associated with an RF transmit signal. A processor is configured to use measurements derived from the measured forward and reverse power output to adjust the RF transmit signal in order to compensate for one or more memory effects of the power amplifier system.

What is claimed is: 
     
         1 . A radio frequency system comprising:
 a radio frequency circuit including a power amplifier configured to amplify a radio frequency transmit signal to generate an amplified radio frequency transmit signal;   one or more memory devices storing a plurality of entries generated during a pre-characterization of the radio frequency circuit under a plurality of characterization states corresponding to different input conditions; and   a processor configured to receive measurements derived from the amplified radio frequency transmit signal, access entries of the plurality of entries based at least in part on the measurements, and, prior to amplification of the radio frequency transmit signal by the power amplifier, adjust the radio frequency transmit signal based on the accessed entries to compensate for one or more memory effects present in the radio frequency circuit.   
     
     
         2 . The radio frequency system of  claim 1  wherein the radio frequency circuit further includes a directional coupler and a plurality of filters positioned between the power amplifier and the directional coupler, the plurality of filters contributing to the memory effects. 
     
     
         3 . The radio frequency system of  claim 1  wherein the plurality of entries are generated using a programmable antenna tuner to tune the radio frequency circuit to desired voltage standing wave ratio points. 
     
     
         4 . The radio frequency system of  claim 1  wherein the radio frequency system does not include an integrated antenna tuner. 
     
     
         5 . The radio frequency system of  claim 1  wherein the radio frequency circuit includes a programmable antenna tuner positioned between an antenna and the power amplifier. 
     
     
         6 . The radio frequency system of  claim 5  wherein the programmable antenna tuner is adjustable to tune an impedance seen by the power amplifier to coarse correct non-linearity within the radio frequency circuit, and the adjustment of the radio frequency transmit signal fine corrects non-linearity within the radio frequency circuit. 
     
     
         7 . The radio frequency system of  claim 1  further comprising an envelope tracking system configured to provide a supply control signal to the power amplifier to control a voltage level of the power amplifier based on a shaped envelope signal, the processor further configured to adjust a delay between the radio frequency transmit signal and the supply control signal based on delay values included in the accessed entries. 
     
     
         8 . The radio frequency system of  claim 1  wherein the radio frequency circuit is implemented in a radio frequency front end module. 
     
     
         9 . A mobile device comprising:
 a radio frequency circuit including a power amplifier configured to amplify a radio frequency transmit signal to generate an amplified radio frequency transmit signal;   one or more memory devices storing a plurality of entries generated during a pre-characterization of the radio frequency circuit under a plurality of characterization states corresponding to different input conditions;   a processor configured to receive measurements derived from the amplified radio frequency transmit signal, access entries of the plurality of entries based at least in part on the measurements, and, prior to amplification of the radio frequency transmit signal by the power amplifier, adjust the radio frequency transmit signal based on the accessed entries to compensate for one or more memory effects present in the radio frequency circuit; and   an antenna configured to transmit the amplified radio frequency signal.   
     
     
         10 . The mobile device of  claim 9  wherein the radio frequency circuit further includes a directional coupler and a plurality of filters positioned between the power amplifier and the directional coupler, the plurality of filters contributing to the memory effects. 
     
     
         11 . The mobile device of  claim 9  wherein the plurality of entries are generated using a programmable antenna tuner to tune the radio frequency circuit to desired voltage standing wave ratio points. 
     
     
         12 . The mobile device of  claim 9  wherein the mobile device does not include an integrated antenna tuner. 
     
     
         13 . The mobile device of  claim 9  wherein the radio frequency circuit includes a programmable antenna tuner positioned between the antenna and the power amplifier. 
     
     
         14 . The mobile device of  claim 13  wherein the programmable antenna tuner is adjustable to tune an impedance seen by the power amplifier to coarse correct non-linearity within the radio frequency circuit, and the adjustment of the radio frequency transmit signal fine corrects non-linearity within the radio frequency circuit. 
     
     
         15 . The mobile device of  claim 9  further comprising an envelope tracking system configured to provide a power supply control signal to the power amplifier to control a voltage level of the power amplifier based on a shaped envelope signal, the processor further configured to adjust a delay between the radio frequency transmit signal and the power supply control signal based on delay values included in the accessed entries. 
     
     
         16 . The mobile device of  claim 9  wherein the radio frequency circuit is implemented in a radio frequency front end module. 
     
     
         17 . A method of processing a radio frequency transmit signal, comprising:
 amplifying a radio frequency transmit signal with a power amplifier of a radio frequency circuit to generate an amplified radio frequency transmit signal;   receiving measurements derived from the amplified radio frequency transmit signal;   accessing entries of a plurality of stored entries based at least in part on the measurements; and   prior to amplification of the radio frequency transmit signal by the power amplifier, adjusting the radio frequency transmit signal based on the accessed entries to compensate for one or more memory effects present in the radio frequency circuit.   
     
     
         18 . The method of  claim 17  further comprising using a programmable antenna tuner to tune the radio frequency circuit to desired voltage standing wave ratio points, and generating plurality of entries at the desired voltage standing wave ratio points. 
     
     
         19 . The method of  claim 17  further comprising adjuring a programmable antenna tuner to tune an impedance seen by the power amplifier to coarse correct non-linearity within the radio frequency circuit, and wherein the adjusting of the radio frequency transmit signal fine corrects non-linearity within the radio frequency circuit. 
     
     
         20 . The method of  claim 17  further comprising:
 controlling an envelope tracking system to provide a supply control signal to the power amplifier to control a voltage level of the power amplifier based on a shaped envelope signal; and 
 adjusting a delay between the radio frequency transmit signal and the supply control signal based on delay values included in the accessed entries.